Mittwoch, 6. Januar 2010

On images of the Mars Reconnaissance Orbiter -MRO- a british research team has discovered possible "spillway" of ancient martian lakes.The pits in the equatorial region of Ares Vallis were first explained as remains of evaporating water ice, but the discovered channels seems to connect different basins, much more like thermokarst- lakes connected by small rivers. The estimated age of the features is with only 3 billion years surprisingly young.

Sonntag, 3. Januar 2010

The cause(s) of the Pleistocene Megafauna extinction is(are) still unclear. Various explanations were proposed, ranging from human activity (hunting or disease spreading) to climate change or sea level rise, and since the last year, a possible extraterrestrial impact. But an important factor until now was less considered - volcanism. Volcanoes can have an impact on climate and ecosystems, for example ash can block the sunlight, and poison large territories.A short, but intriguing paper by Dmitry A. Rubam summarizes and analyze the idea that intensified volcanism at the end of the last glacial period maybe triggered the biotic crisis. The volcanic activity of the last 50.000 years can be reconstructed by ash layers and geochemistry of ice cores, and compared to extinction patterns on the different continents.

The data show a higher frequency of eruptions near the end of the Pleistocene, but the demise of the fauna doesn’t coincide exactly with this period, especially the extinction in Australia happened previously. However it is possible that only a certain "sum" of volcanic events finally triggers a biotic response.

The preliminary results show that intensified volcanism cannot provide a better explanation of the crisis than other triggers; however none of the possible triggers alone provide an ultimate explanation.

The evidence makes it plausible, that an intensification of volcanism just before the end of the Pleistocene was able at least to contribute to the extinction of megafauna in America and Eurasia.

Abo

Just reading

SPÖTL et al.(2006):The last and the Penultimate Interglacial as Recorded by Speleothems From a Climatically Sensitive High-Elevation Cave Site in the Alps. In SIROCKO, F. et al. (ed): The climate of past interglacial. Developments in Quaternary Science 7.